Isoparaffin alkylation process and catalyst for use therein

ABSTRACT

THE CATALYTIC ALKYLATION OF ISOBUTANE WITH AN OLEFIN CONTAINING FROM TWO TO FIVE CARBON ATOMS IS CARRIED OUT USING A CRYSTALLINE ZEOLITIC MOLECULAR SIEVE HAVING A LOW MONOVALENT METAL CATION CONTENT AND HAVING A GREATLY REDUCED CONTENT OF OH EXHIBITING IN FRARED ABSORPTION IN THE REGION FROM 3480 TO 3670 CM.-1.

Patented Mar. 5, 1974 United States Patent Office I CATALYST FOR USETHEREIN Paul Eugene Pickert, Katonah, and Anthony Peter Bol'-' ton,Valley Cottage, N.Y., assignors to Union Carbide" Corporation, New York,NtY. No Drawing. Original application June 26, 1968, Ser. No.

740,049, now Patent No. 3,549,557, dated Dec. 22,

1970. Divided and this application May 6, 1970, Ser.

Int. Cl. C07c 3/52 I US. Cl. 260-68343 10 Claims ABSTRACT OF THEDISCLOSURE The catalytic alkylation of isobutane with an olefincontaining from two to five carbon atoms is carried out using acrystalline zeolitic molecular sieve havingalowmonovalent metal cationcontent and having a greatly reduced content of OH exhibiting infraredvabsorption in the region from 3480 to 3670 cmr' RELATED APPLICATIONS vThis is a division of pending US. application Ser. No. 740,049, filedJune 26, 1968, which issued as US. Pat. 3,549,557 on Dec. 22, 1970. i Y

The present invention relates in general to, the catalyzed alkylation ofan isoparaflin with an olefin'andmore particularly to the alkylation ofisobutane with an olefin having from 2 to 5 carbon atoms. I

Alkylation, as the term is commonly used in the petroleum industry, isthe reaction between an olefin and a branched chain parafiin to obtain ahighly branched chain parafiin having a higher molecular Weight than the isoparalfin employed as the initial reactant., Commercial processesusing strong mineral acid catalysts. alkylate isobutane with C -Colefins to high octane liquid products distilling in the gasoline range.The product alkylate is an ideal fuel for high compression engines,characterized by high anti-knock ratings, excellent tetraethylleadsusceptibility and clean burning characteristics in gasoline blends witholefins and aromatic components. Demand for alkylate is, therefore,increasing' as octane requirements and the need for cleaner burningfuels increases and an improved alkylation process is desired. J I

The mechanism of the alkylation reaction is highly complex and as yetnot completely understood. The primary reaction is illustrated by thecondensation of isobutane with C olefins to yield highly branchedtrimethylpentanes. The product is, however, a 'mixture of the saturatedC isomers and it is necessary for high octane ratings to minimize theproduction of the lower octane dimethylhexanes and monomethylheptanes. I

Numerous side reactions such as hydrogen transfer, disproportionation,cracking and olefin polymerization occur under alkylating conditionsUIhealkylate usually contains a mixture of the isomers of C through C andhigher hydrocarbons. The formation of these by-products is due in partto further reaction of the primary products by dissociation into newparaffins and olefins and the subsequent reactionof these olefins withthe original isoparaffin, or conversely, of the new paraflin with'theoriginal olefin.

Products with greater molecular weight than the primary product areproduced by several reactions and are undesirable since they tend toreduce the vapor pressure of the alkylate and still above the gasolineboiling range. For example, the C primary product of the condensation ofisobutane and C olefin may react with one or two molecules of additionalolefin to yield C and C hydrocarbon product. Similarly, the original C4.olefin may dimerize and trimerize to C and C olefins which then reactwith the isoparaffin. These side reactions are termed polyalkylation andmust be minimized since they result in losses of the primary reactantsin the formation of undesired products. These higher molecular weightproducts are generally separated from the alkylate by fractionaldistillation and added to the gas oil feedstock to catalytic crackingunits.

Polymerization, in which the olefin reactant condenses inter se to yieldan olefinic product, is a very harmful side reaction, since it reducesthe amount of .reactants available for the alkylation reactions andforms accumulations of higher molecular weight residues which rapidlydeactivate the catalyst. Although the lower molecular weight products ofthe polymerization of C -C olefins distill in the gasoline boilingrange, these products are undesirable since they have poor burningcharacteristics and contribute to atmospheric pollution in automobileexhausts. Acceptable alkylate must contain a low concentration ofolefins to meet present-day gasoline specifications.

Polymerization occurs under conditions unfavorable for the rapidreaction of the olefin with the isoparafiin. Such conditions include ahigh ratio of olefin to isoparaflin, a high olefin to catalyst ratio,low catalyst activity and poor mixing of the reactants with thecatalyst. Ease of polymerization increases with molecular weight andbranching with ethylene propylene butene-1 and butene-2 isobutene. Sincethe C olefins are preferred reactants for present-day alkylations,catalysts must be highly active and specific with respect to alkylationand inhibit this competing reaction.

Present-day commercial alkylation processes employ large volumes ofconcentrated sulfuric and hydrofluoric acid catalysts which areimmiscible with the hydrocarbon stream. Reactions are carried outintime-tank or tubular type reactors with strong mechanical agitation toemulsify the acid-hydrocarbon mixture. Reaction times up to 30 minutesare employed after which the emulsion is broken and the acid recoveredand processed for recycle. Refrigeration systems are necessary tocontrol temperature to below about-100 F., generally to below F., duringthe highly exothermic reactions. At higher temperatures acid consumptionincreases and product quality (octane number) is significantly reduced.

Al kylation processes with strong acid catalysts are fraught withdifliculties, requiring careful control of many interrelated processvariables for high-quality alkylate production. Consequently,isoparafiin alkylation is the most costly of the major petroleumrefining processes. Large volumes of isoparafiin and highly corrosiveand difiicult-to-handle acids must be recirculated through complexreactors. Olefin space velocities, that is, alkylate production ratesare low. Catalysts are rapidly deactivated by unconverted olefin and bytrace contaminants in feed streams.'-Continuous acid regeneration andmake-up are necessary. Post-treatment of the alkylate is required toremove traces of dissolved acids and acidic reaction products such assulfate esters and alkylhalides.

Accordingly, it is the general object of the present invention toprovide a novel zeolitic molecular sieve catalyst which has a highdegree of activity and selectivity for the alkylation of isoparaflinswith olefins.

It is another general object to provide a novel process for alkylatingisobutane with an olefin using the catalyst of this invention to producean alkylated product rich in highly branched isoparaifins, low inunsaturated hydrocarbons, and also low in saturated hydrocarbons havingmore than 12 carbon atoms.

It is yet another object to provide a method for preparing the novelcatalyst of this invention.

Other and more particular objects will be readily apparent from thespecification appearing hereinafter and in the appended claims.

The isoparafiin alkylation catalyst of this invention comprises a threedimensional crystalline zeolitic molecular sieve having a pore sizelarge enough to adsorb 2,2,3-trimethylpentane and having a compositionex pressed in terms of mole ratios of oxides as wherein I represents amonovalent metal cation; II represents a divalent metal cation; IIIrepresents a trivalent metal cation; IV represents a tetravalent cation;a has a value of from zero to 0.15; preferably zero to 0.08; b has avalue of from zero to 0.75; c and d each have values of from zero to 1;e has a value of from 2 to 20, preferably 4 to 15; with the proviso thatwhen e has a value of from 2 to 3, the value of (b +c)=0.75 to 1,preferably 0.75 to 0.85 and d=; and with the proviso that when e has avalue of 3 to 4, the value of (b+c+d) =.6 to 1.0, preferably 0.6 to0.85; and with the further proviso that when e has a value of 4 to 20,the value of (b+c'+d) =0.25 to 1.0, preferably 0.45 to 0.75; saidzeolite containing less than about 60 percent, preferably less than 40percent of its maximum OH exhibiting infrared absorption in the regionof 3480 to 3670 cm.-

The catalyst can suitably be prepared from several synthetic crystallinezeolites well known in the art. Zeolite Y is especially preferred, butzeolite X, zeolite -L, zeolite TMAQ and acid treated, i.e., the hydrogencation form of mordenite are also suitable as is the naturally occurringmineral faujasite. A complete description of the composition and methodof preparation of zeolite X, zeolite Y, zeolite L and H mordenite are tobe found respectively in US Pats. 2,882,244, 3,130,007, 3,216,789 and3,375,064. Similar information regarding zeolite TMAQ is disclosed incopending application Ser. No. 655,318, filed July,24, 1967. In thosecases where the zeolitic molecular sieve starting material contains morethan the permissible'lS equivalent percent monovalent metal cations suchas so-' dium or potassium, the monovalent metal cation content can bereduced by conventional ion exchange techniques whereby divalent,trivalent or tetravalent metal cations or monovalent non-metalliccations such as hydrogen or am monium, tetraalkylammonium, [(CH NOH] andthe like which can be thermally decomposed.

Preferably, in the typical case of zeolite Y which contains only sodiumcations in the as-prepared state, the initial base exchange is carriedout using an aqueous ammonium salt solution such as NI-I Cl or NH NO tothe extent that the sodium cations are removed and replaced by ammoniumions to the extent that less than 15 equivalent percent, preferably lessthan 8 equivalent percent, remain. Thereafter, the zeolite is furthercontacted with an aqueous solution of one or more salts of polyvalentmetal cations in proportions and of suitable concentration to exchangethe desired equivalent percent of any residual sodium cations and/ orammonium cations for the polyvalent metal cations.

The monovalent metal cations represented by (I) in the zeolitecomposition formula supra are ordinarily so-- dium or potassium, butother monovalent metal cation such as lithium, rubidium, cesium orsilver are permissible. The divalent metal cations represented by (11)are preferably selected from Group Ila of the Periodic Table (Handbookof Chemistry and Physics, 47th Edition, p. B3, Chemical RubberPublishing Co., U.S.A.) especially magnesium, calcium, strontium andbarium, but manganese, cobaltand zinc can also be used. The trivalentmetal cations represented by (111) of the formula can be aluminum,chromium, and/or iron, and/or also the trivalent rare earth cationslanthanum, cerium, praesodymium, neodymium, samarium, gadolinium,europium, terbium, dysprosium, holmium, erbium, thulium, ytterbium andlutetium. The tetravalent metal cations represented by (IV) areexemplified by thorium and cerium.

To obtain the final zeolite catalyst of this invention the zeoliticmolecular sieve which contains the desired combination of monovalentmetal, polyvalent metal and/or decomposable non-metal and/ or hydrogencations is heated at a temperature of from about 550 C. to 800 C.,usually for a period of from about A: to about 2 hours, under conditionswhich do not permit desorbed water and decomposition products of anydecomposable cations to remain unduly long in contact with the heatedzeolite. A moderate dry air or other inert gas purge stream or a reducedpressure environment over the zeolite mass will suffice. The time andtemperature of heating will vary depending upon the particular zeoliteinvolved, but it is only necessary to remove at least about 40 percentand preferably 60 percent of the OH exhibiting infrared ab sorption inthe region of 3480 to 3670 cm? and retain at least about 75% of thecrystallinity of the zeolite. The determination of when this result hasbeen reached is simply accomplished.' Regardless of the mechanism bywhich the OH here concerned are introduced into the crystal structure,i.e., by the decomposition of an ammonium cation, as a consequence ofpolyvalent metal cation exchange, acid treatment or by any otherpostulated means, the thermally, removable OH content of a givenmolecular sieve is fully developed (i.e. is at its maximum) when thezeolite has been heated to between 300 C. and 400 C. It is onlynecessary to compare the areas under the infrared absorption peaksoccurring in the region of 3480 to 3670 cm. for a zeolite sample heatedat 300 and 400 C. and for the zeolite sample heated at 550 C. to 800 C.to ascertain when at least 40% of these OH have been thermally removed.The areas under the respective curves are proportional to the OHcontent, i-.e.', an area half as large indicates an OH content half aslarge. The necessary infrared analytical techniques are well known tothose skilled in the art.

The percent retention of crystallinity may be determined as the degreeof retention of oxygen adsorption capacity of the zeolite afterdehydroxylation compared to the oxygen capacity upon activation to aconstant weight at 350 C. prior to' the dehydroxylation treatment. Theoxygen adsorption test may be made at mm. 0 pressure at 183 C. afterheating at 400 C. under five microns Hg vacuum for 16 hours.

In general, it has been found that the necessary reduction in the numberof 0H giving rise to infrared adsorption in the region of 3480 to 3670cm. is accomplished by the aforesaid heating of the ion exchangedzeolite at temperatures of from about 550 C. to about 800 C. forsufficient time that at least 75 of the crystallinity of the zeolite isretained and the resulting loss in weight of the crystalline zeoliteupon ignition at 1000 C. for 2 hours is not greater than 2.5%.

It is not necessary to employ in conjunction with the catalysts of thisinvention any additional or conventional catalysts or promoters, but itis'not intended that such compositions be necessarily excluded.Practically any catalytically active metal or compound thereof exceptthe alkali metals can be present either on the external surface or inthe internal cavities of the zeolite or otherwise carried on diluents orbinders used to form agglomerates of the zeolite catalyst. In someinstances elemental metals produce an advantageous result. For example,noble metals of the platinum group used in conjunction with the zeolitecatalyst in a reaction in which ethylene is the starting alkylatingagent, help dimerize the ethylene to butene which is a better alkylatingagent.

Suitable diluent materials include sintered glass, asbestos, siliconcarbide, fire brick, diatomaceous earths, inert oxide gels such as lowsurface area silica gel, silicaalumina cogels, calcium oxide, magnesiumoxide, rare earth oxides and a-alumina, and clays such asmontmorillonite, attapulgite, bentonite and kaolin, especially claysthat have been acid washed.

In the process for alkylating isobutane with an olefin using thecatalyst of this invention, one can utilize a fixed catalyst bed, amoving bed or a fluidized bed and can use the novel catalyst alone or incombination with prior known conventional catalysts. Similarly, althoughit is preferred to alkylate a relatively pure isobutane feed stock,isobutane as the key component in combination with other isoparafiinscan suitably be employed. Advantageously, since a product consisting ofa C hydrocarbon is ideally the sole alkylate product, the feed should beessentially free of isoparafiins having more than 5 carbon atoms or atleast the concentration of these isoparaflins should be small. Theolefinic alkylating agent is preferably a butene, but ethylene,propylene and amylene alone, in admixture with each other, and/ orbutene can be used. In addition to the isoparafiin and olefincomponents, the

- feed stream can also include a nonreactive diluent such as nitrogen,hydrogen or methane.

The precise method of introducing the isoparafiin and olefin reactantsinto the catalyst bed is not a narrowly critical factor provided theisoparaffin/olefin ratio remains high in contact with the catalyst. Thereactants can be combined outside the catalyst bed, or more desirablyprovision is made to add olefin at various points along the bed. Such aprocedure as the latter effectively decreases the tendency of the olefinto polymerize and subsequently crack under the influence of the catalystwith the consequent advantage of reducing catalyst coking and reducingthe formation of undesirably large hydrocarbon molecules in the productalkylate. Such an arrangement also enables one to control thetemperature in the catalyst bed of the highly exothermic reaction.Accordingly, the molar ratio of isobutane to olefin in the reactorshould be maintained within the overall range of about 5 :1 to 50:1.

To a degree, the pressure and temperature conditions in the reactor areinter-dependent, specifically so that at least the isobutane feed is inthe liquid state and preferably both the isobutane and the olefin are inthe liquid state. With this proviso, the suitable temperature range isfrom about 80 F. to 275 F. and the pressure commensurately from about 50p.s.i.a. to 1000 p.s.i.a. The bed throughput of the reactant feed streamin terms of the overall weight hourly space velocity (WHSV) based onolefin is suitably maintained between 0.01 and 2, preferably from about0.05 to about 1.0.

After start-up, the reaction can be run as long as the olefinicunsaturation of the C and higher hydrocarbon product stream is notgreater than Bromine Number 10 (ASTMzD-llSS) 1961. An alternativedetermination of this degree of unsaturation is readily accomplished byhydrogenation techniques well known in the art. At or preferably priorto this point it is desirable to regenerate the catalyst bed to increasethe alkylation activity. Several 6 methods are available for theregeneration depending upon degree of inactivation of the bed and theincrease in activity desired. A moderate regeneration procedure consistssimply of purging cocurrent or countercurrent the bed with isobutane inthe absence of olefin reactant. Another method comprises cutting 01f theolefin feed and heating the bed in the presence or absence of isobutanepurge to at least 25 F. above the reaction temperature. Depressurizationwhile purging, preferably countercurrently, at constant temperature orat elevated temperature can also be employed. In the event the catalysthas been permitted to become seriously coked, an oxidative regenerationcan be resorted to such as that described in US. Pat. 3,069,362 issuedDec. 18, 1962. This procedure in general comprises passing a gas streamcontaining a low concentration of oxygen (usually less than about 2percent) over the coked bed at elevated temperatures at such a rate asto sustain burning of the coke deposit but insufficient to destroy thecrystalline structure of the zeolite. The present invention isillustrated by the following examples. The unsaturation (Bromine Number)of the alkylate product in the examples of this application wasdetermined by a palladium catalyzed hydrogenation procedure employing aBrown Micro Hydro-Analyzer and the results converted to Bromine Number.The Micro Hydro-Analyzer is a commercially available instrument. Theconversion of the H absorption determination to Bromine Number was doneon the basis of 1.0 ml. H (STP)=7.14 mg. Br The grams Br per 100 gramsample is the Bromine Number reported.

EXAMPLE 1.-Preparation of catalyst (A) Hydrated sodium zeolite Ycrystals having a silica to alumina ratio of about 4.8 were slurried inan aqueous solution of ammonium chloride heated to its boilingtemperature and containing a 5:1 equivalent excess of ammonium chloridebased on the sodium content of the zeolite mass. Ion exchange ofammonium cations for sodium cations was permitted to continue for 3hours and then the crystals were isolated by filtration and washed. Theprocedure was repeated five times to reduce the sodium cation content ofthe zeolite to about 5 equivalent percent. Rare earth cations wereintroduced into the zeolite by contacting the ammonium exchanged productwith about two liters of an aqueous solution per pound of zeolite ofdidymium chloride at reflux temperature, the

solution containing about 1 equivalent of the rare earth.

salts based on the zeolite. The resulting zeolite contained about 5equivalent percent sodium cations, about 60 equivalent percent trivalentrare earth cations and the remainder ammonium cations. The zeolitecrystals were filtered and washed to remove chloride ion and dried at110-125 C. in air.

(B) The dried zeolite crystals from part (A) above were calcined in adry air purge at slowly increasing temperatures starting at below 300 C.until the final temperature was 700 C. to give a residual OH in the 3480to 3670 cm. of less than 27% of maximum while crystallinity remainedabove EXAMPLE 2 Using the procedure set forth in Example 1, fourdifferent catalyst compositions were prepared from zeolite Y (SiO /Al O=5.0) incorporating as the polyvalent metal cation species respectivelyAl+++, Mn++, Co++ and Di+++ [Didymium (Di+++) is a commercial mixture ofrare earth metals in the form of chloride salts which containsprincipally lanthanum, neodymdium with lesser proportions ofpraesodymdium, samarium, gadolinium, cerium and ytterbium]. Tabletedforms of these compositions were packed in a fixed bed and employed tocatalyze the alkylation of isobutane with butene-l. The alkylationtemperature was F., the weight hourly space velocity with respect toolefin feed was 0.05, the pressure was 500 p.s.i., and theisobutane/butene-l feed ratio was /1. The results are shown in tabularform below.

an operating temperature of 190 F. and maintaining all other conditionsthe same as in Example 3, the effect of TABLE I C5 in 05+ TMP in CaCations, 0H, product, product, Run equivalent percent Time, wt. wt.Percent Br No. percent of max. hrs. percent percent a yield number n",43.2 2 61 89 72 0. 7 1 Na 5.3 4 49 80 139 6.0 NHH, 46.9 2 6 37 44 1120*, .1 2 59 84 2 Na", 5.3 14 4 44 69 NH4, 46 9 2 Di+++, 2 67 90 3 Ne 5.050 4 60 83 NH4+, 46 0 1 6 49 75 Al 57 2 67 87 4 4 N a 4.5 10 4 59 80 NHr36 0 I 6 44 64 Mn++, 2 67 7e 5 4 Na 7 25 4 58 72 NH4+, 28 I 6 31 45Di"++, 61 2 75 78 6 4 Na 4.6 56 4 67 79 NH 32.1 1 6 69 83 1 Having IRstretching frequencies between 3,480 and 3,670 cm I Before calcination.

8 Trimethyl pentane.

4 WHSV=.10, temp.=190-200 F.

EXAMPLE 3 The effect of operating temperature in the catalyst bed isshown in the data of Table II below. The sole zeolite catalyst employedwas a zeolite Type Y having a silica/ alumina ratio of 5.0 andcontaining 59.5 equivalent percent didymium and 34.2 equivalent percentammonium cations prior to calcination at 630 C. The zeolite aftercalcination contained less than 38% of the maximum OH having infraredstretching frequencies in the range of 3480 to 3670 cmr The weighthourly space velocity based on olefin was 0.05, the feed was isobutaneand butene-l in a ratio of 20:1 and the pressure was maintained at 500p.s.i.

TABLE II Reaction Percent Percent Percent Bromine temp., F. Hours 0 TMPin 0 yield number In 05+ traction. "WHSV=0.1.

EXAMPLE 4 Using the same catalyst composition as in Example 3,

varying the weight hourly space velocity is shown in tabular form below.

TAB LE III Percent Percent Percent Bromine WHSV Hours a P in 0; yieldnumber 0.1 2 73 89 122 1.3 4 68 82 229 e 66 as 219 1.0 0.2 2 70 80 1491.0

0.4 2 62 75 131 3.7 t 22 it 33 55 0.8 2 58 81 76 11.4 4 49 5 54 6 46 v026 64 EXAMPLE 5 In the series of experiments, the olefin flow rate washeld constant and the amount of isobutane regulated to obtain thefollowing isobutane/olefin ratios: 10/1; 20/ 1; and 30/ 1. The dataobtained, given in the following table, shows that operating at anisobutane/butene-l ratio of 20/1 is a significant improvement over the10/1 ratio. The amount of C in the product is maintained over a longerperiod and the C concentration is reduced after six hours from 19% to8%. The amount of trimethylpentanes in the C3 fraction, as well as theoverall yield, increase significantly. The temperature employed in theexperiments was approximately F. The catalyst was the same as used inExample 3.

TABLE IV In alkylate product Isobutane/ Percent Percent Percent Yield,olefin C3 12 TMP in 0; percent 9 EXAMPLE 6 To demonstrate the effect ofcalcination temperature in the preparation of thefinal catalystcomposition from the ammonia and polyvalent cationexchanged form of thezeolite, a mass of dried zeolite Y tabletshaving a SiO /Al O ratio of5.0, 63 equivalent percent rare earth cations (didymium), 28 equivalentpercent .ammonium cations and 5 equivalent percent sodium cations wascalcined in dry air at different temperatures for 2. hours. Theresulting zeolite materials were thereafter employed as alkylationcatalyst in a system operated at 500 p .s.i. 80-100 F. and WHSV of 0.1for a feed stream of isobutane-butene-l mixture in the ratio of /1. Theresults are shown intabular form below:

TABLE V Product analysis Residual Percent Calcination OH Hrs. on PercentPercent TMP temp., C. retention stream Ca C12 in C 1 arso aevo crnr 1Less than 75% crystallinity retained.

At 650 C., when the atmosphere in which the zeolite is calcined ischanged from dry air to steam at atmospheric pressure, the productalkylate from theotherwise same system as in Table IV contained only 32percent C of which only 11 percent was trimethylpentane.

Operation at 200 F. aids substantially in the desorption of the alkylatethus preventing subsequent polyalkylation to a great extent. Theremaining polyalkylate can be removed further by either temperature orpressure swing or both simultaneously. In temperature swing, after acertain predetermined catalyst activity decline, the olefin feed isstopped and the reactor temperature raised to enhanoe desorption. Thedesorbed polyalkylate can be swept out by the isoparaflin flow. Afterdesorption, the temperature is lowered to reaction temperature andolefin feed 10 The catalyst is therefore essentially deactivated. Theolefin flowwas stopped, and temperature raised to 600 F. with iC flow.The temperature was then lowered to reaction temperature and feedrestored.

Alkylate yield, wt. Wt. percent Wt. percent based on percent TMP Brolefin 0 -01 in product number Thus the temperature swing has allowedactivity recovery.

Similar advantageous results are obtained using the aforesaid procedurewith inert gas (hydrogen) purge rather than isoparaflin.

For pressure swing regeneration, after or prior to catalyst deactivationhas taken place, the reactor is depressurized and a partial vacuum maybe applied to remove the polyalkylate; a liquid or gas purge may be usedto assist the removal, The system is then pressurized again and reactionstarted. The polyalkylate formation can be controlled or suppressed byperiodic solvent wash of the bed before substantial deactivation takesplace. A number of solvents can be used. Isobutane is advantageouslyused as it is conveniently available as one of the reaction species. Inthis scheme, the reaction is allowed for a length of time, the feed isthen stopped and the bed subjected to a solvent Wash or purge. Twomethods of solvent wash are available, namely, cocurrent wash andcountercurrent wash. In cocurrent Wash, the feed and the wash solventboth travel in the same direction. The solvent then successively movesthe residual alkylate down the bed. That such scheme enhances catalystlife and selectivity can be seen from the following example, in whichcatalysts of this invention containing 61 equivalent percent rare earthcations and 4.6 equivalent percent sodium cations had been activated tocontain -57 percent residual OH exhibiting infrared adsorption in the3480-3 670 cm. range, were employed for the alkylation of isobutane withbutene. WHSV=0.1; iC /C ==20; 500 p.s.i.g.; 200 F.

EXAMPLE 8. Solvent wash regeneration No regeneration Cocurrent washregeneration l 1 Each 1 hour reaction period was followed by hr. wash.

restored. The successful use of temperature swing in catalystregeneration is illustrated by the following example.

EXAMPLE 7-Temperature swing regeneration Alkylate yield, wt. Wt. percentWt. percent based on percent '1 P Br olefin (35-010 in product numberThese results show that with the cocurrent wash, the catalyst stabilityas well as selectivity for better alkylate had improved.

In countercurrent wash, the wash solvent travels countercurrent toreactant flow. The desorbed alkylate thus exits at the inlet side of thereactor and cannot foul up the cleaner sections of the bed. The catalystlife therefore will be further improved before supplementary methods ofregeneration are needed. A countercurrent wash regeneration canadvantageously be combined with a moving bed reactor in which thecatalyst enters at the top of the reactor, moves down the bed; at thelower end of the bed a countercurrent stream of isoparaflin washes outthe polyalkylate. The combined product-wash eflluent stream of nearlyconstant composition goes to separation. The catalyst is recycled to thetop. A slip-stream of catalyst may be withdrawn and subjected to anoxidative burn-off if necessary.

1 1 EXAMPLE 9 This example shows the etfect of regeneration bydepressurization and high temperature gas purging. The catalyst employedwas zeolite Y having a SiO /.Al O ratio of 5 which had been ionexchanged to contain 63 equivalent percent didymium cations and 28equivalent percent ammonium cations and then calcined at 680 C. to 700C. Thefixed bed reaction conditions were 500 p.s.i.g. pressure, 90 F.temperature, a WHSV of 0.2 and a molar isobntane to butene-l ratio of10.

A control sample was evaluated over a period of eight hours withoutregeneration. Other samples, A and B, were evaluated for four hours,after which they were regenerated by depressurization to atmosphericpressure and purging with hydrogen at moderate and high temperature; theregenerated catalysts were then put on stream for a further four hours.

It will be readily apparent from the foregoing examples that periodicregeneration of the catalyst at frequent intervals while theunsaturation of the product stream is still inside the preferred maximumis a most desirable mode of operation.

What is claimed is:

1. Isoparafiin alkylation process which comprises con- 05+ percentPercent Percent Percent Sample number yiel C a C TMP in Control Initial4 hr. sample 81. 9 66. 3 10. 25 81. 88 Final 4 hr. sample 32. 1 32. 349. 6 32. 1

A Initial 4 hr. sample- 81. 4 63. 7 9. 9 80. 95 4 hr. sample afterregen- 30. 1 46. 4 21. 5 65. 7

eration at 100 C.

B Initial 4 hr. sample 83. 6 67. 7 9. 3 80. 3 75. 5 61. 0 11. 4 76. 4

4 hr. sample after regeneration at 400 C.

These data show that the higher temperature regeneration almost producesthe original catalytic activity and selectivity. The absence ofregeneration results in loss of both activity and selectivity.

EXAMPLE This example compares the performance of the catalyst of Example8 in unbonded diameter tablet form and as a composite containing aninert diluent as bonding agent. The composite was formed by thoroughlywet mix- :ing 75-80 wt. percent of the zeolite powder with 25 Wt.percent bentonite clay and extruding as a A diameter by 54 longparticles. Both the tablets and the composite were dried and calcined at630 C. before use in alkylation reaction. The following results wereobtained at process conditions of: Pressure, 500 p.s.i.g.; Temp., 190F.; i-C /C =-1 molar ratio, 20; WHSV, 0.1.

Percent Percent Time Ca in C12 in Percent Percent Catalyst (hrs.)alkylate alkylate yield TMP in Ca Extrudate 2 75. 4 4. 2 79. 2 6 67. 16. 4 178 75. 9

Tablets 2 7o. 1 4. a so. 5 6 60. 2 8. 7 114 69. 3

These data show that the composite containing the binder with only 75-80wt. percent active catalyst content EXAMPLE 11 This example illustratesthe importance of reducing the sodium cation content to a value of lessthan 15 equivalent percent, preferably to a value of less than 8equivalent percent. Catalyst samples were prepared as in Example 1containing various sodium levels by controlling the extent of ammoniumexchange. They were each tested under the same process conditions at atemperature of about 80 F. The following results were obtained.

tacting isobntane with an olefin containing from 2 to 5 carbon atomsinclusive and a catalyst comprising a threedimensional crystallinezeolitic molecular sieve having a pore sizelarge enough to adsorb2,2,3-trimethylpentane and having a composition expressed in terms ofmole ratios of oxides of wherein I represents a monovalent metal cation;11 represents a divalent metal cation; III represents a trivalent metalcation; IV represents a tetravalent cation; a has a value of from zeroto 0.15; b has a value of from zero to 0.75; c and d each have values offrom zero to 1; e has a value of from 2 to 20; with the proviso thatwhen e has a value of from 2. to 3, the value of (b+c) =0.7S to 1 andd=0; with the proviso that when e has a value of 3 to 4, the value of(b+c+d)=.6 to 1.0; and with the further proviso that when e has a valueof 4 to 20, the value of (b+c+d) =0.25 to 1.0; said zeolite containingless than about 60 percent of its removable OH exhibiting infraredabsorption in the region of 3480 to 3670 cm. said contact of catalyst,isobutane and olefin being at a temperature of from about F. to about275 F. and at a pressure commensurate therewith to maintain at least theisobntane in the liquid state and the molar ratio of isobutane to olefinbeing from about 5:1 to 50:1.

2. Process according to claim 1 wherein the zeolitic molecular sievecatalyst contains less than 40 percent of its maximum OI-I exhibitinginfrared adsorption in the region of 3480 to 3670 cmr 3. Processaccording to claim 1 wherein a has a value of from zero to 0.08 and ehas a value of from 4 to 15.

4. Process according to claim 1 wherein any decrease in the alkylationactivity of the zeolitic molecular sieve catalyst is at least partiallyrestored by regeneration thereof prior to the time at which the olefinicunsaturation of the alkylene product having at least 5 carbon atomsbeing then produced has a bromine number of 10.

5. Process according to claim 4 wherein themethod of catalystregeneration comprises purging the catalyst with n inert saturatedhydrocarbon solvent for the poly- 13 alkylate being no more highlybranched than 1 branch chain per 4 carbon atoms, said purging being donein the substantial absence of olefin.

6. Process according to claim 4 wherein the method of catalystregeneration comprises heating the catalyst in the substantial absenceof olefin at a temperature at least 25 F. above the temperature obtainedduring the isO- butane alkylation reaction.

7. Process according to claim 6 which includes the additional step ofpurging the catalyst with an inert gas.

8. Process according to claim 4 wherein the method of catalystregeneration comprises reducing the pressure over the catalyst to desorbat least some of the adsorbate thereon.

9. Process according to claim 8 wherein the depressurization isaccompanied by an inert gas purge of the catalyst. i

10. Process according to claim 9 wherein in addition to saiddepressurization and inert gas purging the temperature of the catalystmass is increased.

References Cited UNITED STATES PATENTS 3,236,761 2/1966 Rabo et a1.252-455 Z 3,236,762 2/1966 Rabo et al. 260-68343 3,251,902 5/1966Garwood et a1. 260683.43 3,312,615 4/1967 Cramer et a1. 260683.43

DELBERT E. GANTZ, Primary Examiner 5 G. J. CRASANAKIS, AssistantExaminer

